The US Supreme Court has declined to review the challenge by Alaska against the EPA's rejection of the Pebble mine project.
The decision effectively upholds the ruling by the EPA, which had previously issued a pre-emptive veto against the proposed mine, citing environmental concerns.
The Pebble Mine, owned by Northern Dynasty Minerals, has been touted as the world's largest undeveloped copper, gold and molybdenum project.
Despite having the support of the Alaskan State Government, the project faced significant opposition.
It is located in the Bristol Bay watershed, home to the world's largest sockeye salmon fishery and 25 federally recognised indigenous communities, CNN reported.
The EPA's final determination in January 2023 to prohibit the mine's construction was based on the potential risks it posed to the Bristol Bay salmon population.
The agency's decision to restrict the disposal of construction and mine waste within the watershed was seen as a decisive move to protect the environment and the subsistence needs of the local communities.
Alaska’s attempt to overturn the EPA's decision reached the Supreme Court after the state argued that the nation's highest court had the jurisdiction to review the case before it was considered by lower courts.
However, with the Supreme Court’s refusal to hear the challenge, the EPA’s ruling stands, effectively vetoing the Pebble Mine project.
The controversy surrounding the Pebble Mine has spanned approximately two decades, with widespread criticism from various interest groups across Alaska and other states, as well as opposition from many Alaskans themselves.
Northern Dynasty’s Pebble Limited Partnership CEO John Shively said: “While it is a disappointing decision, it is important to note that this is not a comment on the arguments put forward by the state.
“We have long stated our belief that the EPA has acted outside of its regulatory authority and that remains our position today. The legal issues raised by the state will now work their way through the federal courts.
“We will also evaluate our legal options in contesting the extraordinary steps the EPA has taken to pre-emptively stop the Pebble Project. Pebble is an important project for Alaska and the nation.
“It could create jobs for Alaskans, provide an economic catalyst for the state and provide a much-needed source of critical minerals for the long-term safety and security of the United States.”